Designing a Series of Emails

When our vice president of global human resources, Tinna Hall, requested a set of email teasers to promote our company-wide employee engagement survey, I had these concerns: how will I carry a consistent theme across all emails? How can I design a flexible format that will effectively communicate the content of each message visually? How do I keep them interesting to our 1,000-plus designers? And lastly, as a member of "branding police" for Affinity Express, how will I accomplish all of this while staying true to our branding?